The present invention concerns a signal processing method for a wide band digital radio receiver and a reception architecture for implementing said method. It can be applied in particular in the field of mobile telephone terminals or television receivers.
The multiplication of standards, especially in telecommunications and more particularly in cellular telephone applications, has forced manufacturers to design specific products for each type of network. The current trend is thus to find a single product, the adaptation of this product to the network being effected by software.
Thus, the embodiment of a universal digital radio able to support all the demodulation diagrams and the most diverse protocol evolutions via a simple updating of the processing software of a numerical processor (DSP) constitutes the main objective of the software radio. Having regard to the technical improvements in the field of numerical processors and analog/digital converters, the software radio aims at digitalising the signals as close as possible to the antenna and designing a generic material portion.
One of the brakes for applying this techniques is the analog/digital converter. In fact, the best solution would consist of directly digitalising the signals at the output of the antenna. Unfortunately, the current technology of A/D converters does not make it possible to work at high sampling frequencies with sufficient dynamics and sensitivity to directly digitalise the signals at the output of the antenna. There are A/D converters able to sample at 1 Gigasample per second, but their resolution is limited to 8 bits in the best of cases which is clearly inadequate to recover GSM signals (200 KHz channel width and 90 dB dynamics) in a wide band of frequencies of about several hundreds of megahertz.
At the current moment, the only solution to simulate a software radio and thus process all the radio signals in a wide band of frequencies consists of stacking the narrow band digital receivers. However, this solution is not very satisfactory as it proves to be extremely expensive and does not support evolutions of standards.